1. Technical Field
The present invention relates to a manufacturing method of a semiconductor device and a substrate processing apparatus for processing a plurality of substrates by using a processing gas of different gas species.
2. Background Art
A thermal chemical vapor deposition method (thermal CVD method) is given as an example of a manufacturing method of a semiconductor device. By this thermal CVD method, two kinds or more of processing gases of different gas species are used to form a thin film on a substrate such as a wafer. Particularly, when a plurality of substrates are collectively processed, the processing gases of different species are supplied into a processing chamber heated to a film forming temperature, and thin films are simultaneously formed on the plurality of substrates. When a nitride silicon film is formed as the thin film, the processing gas containing silicon (Si) and the processing gas containing nitrogen (N) are thermally decomposed to precipitate nitride silicon on the substrate (for example, see patent document 1).
FIG. 4 is a schematic block diagram showing an example of a processing furnace of a substrate processing apparatus for simultaneously forming the thin film on the plurality of substrates. This substrate processing apparatus is constituted of, for example, a vertical pressure reducing CVD device. This processing furnace 5 includes a heater 3 and a reaction tube 4. A boat 8, on which a plurality of wafers 9 are stacked, is loaded into a processing chamber 2 formed in the reaction tube 4. A gas supply system 1 for supplying the processing gas of different gas species or inert gas into the processing chamber and an exhaust system 7 having a pump 6 for exhausting an inside of the processing chamber 2 are provided in a processing furnace 5.
It is general to use one system nozzle in which every one nozzle is provided for each processing gas. In this one system nozzle, every one nozzle for deposition processing is provided for each processing gas. The one system nozzle is provided on an upper stream side (lower part of the processing chamber 2) of a gas flow outside of a region in which a plurality of wafers 9 exist. Accordingly, each processing gas is supplied from each one place in the lower part of the processing chamber 2, toward the plurality of wafers 9 stacked on the boat 8.    Patent document 1: Japanese Patent Laid Open No. 2004-95940
Here, when there is a small number of substrates to be processed, or when the substrate to be processed is a small diameter substrate, the thin film having an excellent deposition characteristics can be formed on the substrate by using the aforementioned substrate processing apparatus. This because, a surface area of the substrate on which the thin film is formed is small, and therefore a flow rate of the processing gas required for deposition, namely, the flow rate of the processing gas required for covering a substrate surface area can be covered by using the aforementioned processing furnace even under a reduced pressure.
However, when there is a large number of substrates to be processed, or when the substrate to be processed is a large diameter substrate having a high pattern density, the surface area in which the thin film is formed is increased. In this case, in the aforementioned substrate processing apparatus, the processing gas of a specific amount or more of flow rate needs to be supplied into the processing chamber from one place. However, there is an exhaust resistance in the processing chamber, and therefore when the processing gas of a specific amount or more flow rate is supplied from one place, the pressure in the processing chamber is increased, thus making it difficult to reduce the pressure of the processing chamber to deposit a film.
Therefore, when the film is deposited by reducing the pressure in the processing chamber, the flow rate of the processing gas needs to be restricted to a specific amount or less of flow rate. However, the processing gas is gradually consumed for depositing the film, toward a stacking direction in which a plurality of substrates are stacked (from an upper stream side to a lower stream side). Therefore, when the flow rate of the processing gas is restricted to a specific amount or less, an amount of the processing gas supplied to the substrate that exists on the lower stream side of the gas flow out of the plurality of substrates becomes gradually insufficient. Accordingly, when the thin film formed from an amorphous material obtained by chemical reaction by using two kinds or more of different gas species, particularly, the deposition characteristics such as a practical film thickness uniformity can hardly maintained. Note that in order to suppress an increase of the surface area of the substrate on which the thin film is formed, it can be considered that the number of wafers is made small. However, in this case, the number of wafers that can be collectively processed is also reduced, thus deteriorating productivity of the substrate processing apparatus itself. Namely, when the plurality of substrates are processed by using the processing gas of different gas species, the following phenomenon occurs. Namely, the productivity is lowered when the deposition characteristics is prioritized, and when the productivity is prioritized, the deposition characteristics are deteriorated. Particularly, when the thin film of a large diameter having a high pattern density is deposited, this tendency becomes remarkable.
An object of the present invention is to provide the manufacturing method and the substrate processing apparatus capable of realizing a high productivity, while maintaining excellent deposition characteristics in a case of using the processing gas of different gas species.